We have previously presented evidence that chemotactic factors induced neutrophil responsiveness is initiated by increases in the cytoplasmic levels of calcium. More recently, on the basis of indirect evidence, we have postulated that arachidonic acid and/or its metabolites may mediate the mobilization of calcium by chemotactic factors. The specific aim of this application is therefore to critically, and directly, examine this hypothesis. To this end, the following set of experiments will be carried out. 1) The effects of exogeneous arachidonic acid and of its metabolites on the previously described pool of intracellular mobilizable calcium and on the plasma membrane permeability to cations will be examined in detail (concentration, time, stereo specificity). 2) The functional responses (granule enzyme release and aggregation) evoked by the above mentioned fatty acids will be defined. Particular attention will be paid to correlate cation (and calcium in particular) movements and functional responsiveness. 3) The effects of arachidonic acid metabolism inhibitors on the chemotactic factor and the fatty acids induced cation movements and cell responses will be further examined. 4) The relationship between the fatty acids and the chemotactic factor induced functional responses and ion fluxes will be assessed. This will include, among others, the examination of the simultaneous addition of each of the two kinds of stimuli, and the preincubation with either one of them (deactivation), on the subsequent responsiveness of the cells. The above approach, patterned after the classical second messenger criteria, will help define the early events of the excitation-response coupling sequence in rabbit neutrophils. In addtion, as lipoxygenase metabolites of arachidonic acid are known to evoke contractile and secretory responses in various cells and tissues (e.g. SRS-A), the mechanism proposed here may be applicable in cells such as mast cells and smooth muscles. The studies proposed in this application may therefore be relevant to a basic understanding of the symptoms of several pathological conditions such as rheumatoid arthritis, asthma, immediate hypersensitivity and the anaphylactic shock.